This invention relates to tufting machines for producing tufted textile goods such as carpet, upholstery and the like and more particularly to a hollow needle tufting machine of the type disclosed in U.S. Pat. Nos. 4,549,946; 4,991,523; 5,080,028; 5,158,027; 5,165,352; 5,205,233 and 5,267,520 and is an improvement over the apparatus and methods disclosed therein.
U.S. Pat. No. 4,549,946 discloses a tufting apparatus of this type for producing patterned tufted goods using yarns of different colors or different textures. This apparatus is capable of placing yarn into a backing to create patterns and designs which were then previously generally available only from a weaving loom or by using printing techniques. The apparatus employed multiple heads spaced across the width of a backing material. Each head included a reciprocating hollow needle for penetrating the backing and for implanting yarn tufts into the backing by feeding yarn through the needle pneumatically. The needle is connected to a yarn exchanger into which a plurality of yarns of different colors, for example, are supplied and a mechanism is included which enables a selection of a yarn for implantation into the backing for each penetration by the needle. The multiple heads were stepped in synchronism across the backing for a distance corresponding to the spacing between the heads in order to implant a transverse row of yarn tufts. The backing was then advanced to the position of the next row and the process repeated to implant the next row. A computer controlled the selection of the yarn implanted by each needle for each penetration of the backing in order to produce a desired pattern in the finished goods.
A significant factor influencing the production speed of practical apparatus employing the aforesaid patented disclosure is the number of tufting heads embodied in the apparatus. The greater the number of heads, the less distance each head had to traverse and, accordingly, the faster a row of tufts could be implanted into the backing. As the number of heads increased, however, other problems arose. The increased weight made it more difficult to move the heads accurately and to maintain their alignment and positions relative to one another. Thus, rather than the multiple heads which carry the hollow needles being moved across the backing, U.S. Pat. No. 4,991,523 proposed that the backing rather than the heads be shifted transversely to move substantially less weight. Not only did this simplify the transverse shifting apparatus but also provided greater speed and accuracy to the yarn placement.
The shifting of the backing material results in a number of transversely spaced stitches produced by each needle, the spacing between adjacent stitches or tufts being equal to the stitch gauge of the product produced. For example, if the needles are spaced apart by two inches, as has been and remains the case in the machines produced using the disclosures of the aforesaid patents, and the gauge or space between adjacent stitches is 1/10 inch, the backing is shifted a total of 20 steps from the first penetration of the backing by a particular needle to the last penetration of the backing by that needle before the fabric is shifted in the opposite direction. Accordingly, if the needles could be spaced apart by less than the two inches mandated in the prior art in view of the number of feed mechanisms involved, i.e., a separate feed mechanism for each yarn for each needle, then the number of shifts required to be made by the fabric would be less and therefore the time required to produce a fabric of a given length would be reduced. This, of course, translates into an increased speed of operation, speed being a major drawback of machines in the prior art.
Another significant factor influencing the cost and accuracy of this type of tufting apparatus is the control over the feeding of the yarn to the hollow needles. The feeding of the yarn must be positive, and when a yarn change is to be made for a particular needle, the yarn previously stitched by the needle has to be positively withdrawn from the needle so that the subsequent yarn will not be blocked by the previously sewn yarn. Unless this withdrawal of the previously sewn yarn in the prior art apparatus and method is assured, a substantially greater air pressure is required to supply the subsequent yarn through the needle. Furthermore, when the yarn is withdrawn from the needle, unless the yarn withdrawal is controlled, the next time that yarn is required to be fed to the needle an accurate and consistent length of yarn can not be assured. This would also result in requiring additional air pressure to assure that a sufficient length of yarn is supplied. The effect is that a greater than required amount of pressure must be utilized, and if too much yarn is supplied to the needle additional yarn shearing operations are required for producing a satisfactory product. Accordingly, in U.S. Pat. No. 5,080,028 a pullback mechanism is disclosed which is disposed between the yarn feeder and the hollow needle, the pullback mechanism acting to pull the yarn a preselected amount from the needle so that the yarn passageway in the needle is not restricted by the previous yarn when a subsequent yarn is to be sewn. Additionally, to assure that the pullback mechanism draws the yarn from the needle and not from the yarn supply or the feed roller, clamping apparatus had to be disposed between the yarn feed roller and the pullback mechanism to positively clamp the yarn when the yarn change is to be made. The pullback mechanism is thereafter activated and the yarn feed roller ceases positive feeding of the yarn. Thus, the yarn pullback mechanism draws a predetermined amount of yarn from the needle maintaining it in reserve until again required. Additionally, the yarn feed roller as it ceases positive feeding draws a preselected amount of yarn from the yarn supply for subsequent use when needed. When the needle is to commence stitching with a particular yarn, the yarn feed roller is activated and the yarn clamping apparatus and yarn pullback mechanism are deactivated.
A further significant factor affecting the efficiency and cost of the aforesaid apparatus and its operation is the amount of pressurized air that must be supplied to feed a selected yarn through the system from the yarn injectors which receive the yarn associated with a respective needle and directly on through separate passageways to the yarn exchanger in which yarn exchange occurs. In the early machines, air was supplied to a plenum from which air was directed to a tapered space leading into each yarn carrying conduit extending to the yarn exchanger. Air was thus constantly supplied to the plenum under high pressure to drive the yarn fed by the yarn feed rollers. This resulted in a substantial amount of wasted air and the system was thereafter modified. Air flow was then regulated and controlled so that air under a high pressure was only supplied to a passageway having the selected yarn for injection into and through the needle, while air under a low pressure is supplied to the other passageways. Thus, both low and high pressure air flows into the funnel of the yarn exchanger. This, however, resulted in a turbulence so that the various yarns became entangled, and this problem was in turn solved by disposing an air jet in the yarn exchanger adjacent to the entry to the needle for blowing air into the needle inlet to prevent the selected yarn from being diverted and tangled with one or more of the other yarns.
The yarn exchanger in these machines has the form of a funnel with each yarn adapted to enter the enlarged end through a separate passageway and the air jet is in the form of a nozzle disposed for blowing the selected yarn into the needle. The selected yarn is fed to the needle by high pressure air within its passageway while low pressure air flows through the other passageways. Accordingly, a substantial amount of air under pressure to must be directed into the yarn exchanger funnel.
With all these changes the method and apparatus heretofore discussed still retains major drawbacks that substantially and significantly limit its acceptance. First and foremost is the slow production rates because of the spacing between adjacent needles, and the other major drawback is the high energy consumption and noise levels due to the large amount of compressed air that must be utilized for the aforesaid reasons. The high air consumption has also been a limiting factor toward increasing production rates by precluding an increased number of hollow needles per machine.
Thus, it may be seen that there has always been a need for greater speed and thus production efficiency for these hollow needle tufting machines and that there is a need to reduce the amount of air required by the machines to reduce production cost. Additionally, not only does the large air flows require large compressors, but the noise levels associated with these air flows is great.